U-boat

A submarine operated by Germany, especially in the First or Second World War. U-boats became known for attacking Allied shipping across the Atlantic.

Diesel-electric transmission: A propulsion system in which a diesel engine generates electricity for motors that turn a vehicle’s propellers. U-boats used diesels on the surface and electric motors while submerged.
Imperial German Navy: Germany’s navy from the unification of the German Empire in 1871 until the end of the First World War. It built and deployed the first German U-boat fleet.
Battle of the Atlantic: The prolonged campaign between the Allies and Axis powers to control Atlantic sea routes during the Second World War. U-boats were central to the Axis effort to sever Allied supply lines.
Hedgehog (weapon): A British forward-throwing anti-submarine mortar introduced during the Second World War. It gave escorts a way to attack submerged U-boats while maintaining sonar contact.
Royal Navy Submarine Service: The submarine branch of the United Kingdom’s Royal Navy. It operated against German U-boats while also conducting its own submarine campaigns.
Torpedo: A self-propelled underwater weapon designed to strike ships or submarines. Torpedoes let U-boats attack ships without surfacing to use deck guns.
U-1 (German submarine): The first submarine commissioned into the Imperial German Navy, entering service in 1906. Its commissioning marked the start of Germany’s operational U-boat service.
Battle of the Atlantic (1939–1945): The Second World War campaign in which German U-boats attacked Allied shipping across the Atlantic. It was the defining operational setting for the Second World War U-boat fleet.
Enigma machine: An electromechanical cipher machine used by Germany to encrypt military communications. Allied decryption of naval Enigma traffic helped locate U-boats and reroute convoys.
United States Navy submarine force: The submarine warfare branch of the United States Navy. Its Pacific campaign differed sharply from Germany’s Atlantic commerce war.

Linked from 4 pages